Photo Shop A charges $1.60 to develop a roll of film plus $0.11 for each print. Photo Shop B charges $1.20 to develop a roll of film plus $0.13 per print.

Question

For how many prints will the amount spent at each photo shop be the same? What will be that amount?

Answer 1

For shop A, it costs $1.60 to develop plus $0.11 each print, so we can come up with the equation:

 

y = 0.11x + 1.60

 

where y is the total amount spent, and x is the amount of prints made.

 

For shop B, it costs $1.20 to develop and $0.13 per print, so we can come up with:

 

y = 0.13x + 1.20

 

To find out how many prints it will take at each for the price to be the same, you set the equations equal to each other and solve for x:

 

0.11x + 1.60 = 0.13x + 1.20

0.11x + 0.40 = 0.13x

0.40 = 0.02x

20 = x

 

So it will take 20 prints at either shop for the price to be the same.

 

To find the amount, plug in 20 for x in one of the equations:

 

y = 0.11x + 1.60

y = 0.11(20) + 1.60

y = 2.20 + 1.60

y = 3.80

 

And it will cost $3.80.